U.S. patent number 4,781,547 [Application Number 06/930,586] was granted by the patent office on 1988-11-01 for gas equalizer for downhole pump.
Invention is credited to Raymond D. Madden.
United States Patent |
4,781,547 |
Madden |
November 1, 1988 |
Gas equalizer for downhole pump
Abstract
A gas equalizer device for use in conjunction with a
reciprocatory pump located downhole in a wellbore. The device of
the present invention avoids a condition commonly known in the
pumpjack art as "fluid pounding", which is brought about when
compressible gases accumulate in the working chamber of the
downhole pump. The gas equalizer device of this invention includes
a pushrod having a marginal end reciprocatingly enclosed in a
slidable manner within a housing which is mounted to the usual
traveling valve cage of the downhole pump. The pushrod is
alternately moved from an extended into a retracted position each
upstroke and downstroke of the pump. The free terminal end of the
pushrod is arranged to engage the ball check valve of the traveling
valve assembly as the pump commences the downstroke. This unseats
the ball, thereby allowing any accumulated gases to escape from the
variable pump chamber. This action allows the escaped gases to flow
out of the pump and up the tubing string along with the produced
fluid and thereby avoids the undesirable gas locking that otherwise
may occur.
Inventors: |
Madden; Raymond D. (Mansfield,
TX) |
Family
ID: |
25459487 |
Appl.
No.: |
06/930,586 |
Filed: |
November 13, 1986 |
Current U.S.
Class: |
417/444; 417/514;
417/554 |
Current CPC
Class: |
F04B
47/02 (20130101) |
Current International
Class: |
F04B
47/02 (20060101); F04B 47/00 (20060101); F04B
007/00 (); F04B 021/04 () |
Field of
Search: |
;417/435,443-447,511,514,554,53 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Neils; Paul F.
Attorney, Agent or Firm: Bates; Marcus L.
Claims
I claim:
1. A gas release device for use in conjunction with a downhole pump
of the reciprocatory type that includes a traveling valve assembly
having a ball type valve element; said gas release device includes
only an adaptor means; a cylindrical main body; a piston assembly;
and, a pushrod;
said adaptor means enables said main body to be attached directly
to the traveling valve assembly of the pump, a passageway formed
through said main body and along the central longitudinal axis of
the pump, said pushrod has a free end which extends into said
passageway for engaging the ball of the traveling valve assembly,
and an opposed end is directly and rigidly attached to and forms
part of said piston assembly; said main body has an upper end
opposed to an enlarged lower end formed thereon;
said piston assembly has an upper cylindrical skirt member which is
rigidly attached to said port sub; passageways formed through said
port sub through which production fluid flows each downstroke of
the pump and thereby reciprocates the piston assembly towards the
traveling valve; opposed faces formed by an inwardly directed boss
of the cylindrical skirt member and the lower enlarged end of said
main body abuttingly engage during each upstroke;
whereby; the free end of said pushrod lifts the ball of the
traveling valve each downstroke of the well pump.
2. The gas release device of claim 1 wherein said downhole pump has
a traveling plunger and a seat that receives the ball, said
traveling valve is mounted on said traveling plunger at a location
whereby said ball thereof is lifted from the seat thereof by the
free end of the pushrod during each downstroke of the pump.
3. The gas release device of claim 1 wherein said downhole pump
includes a traveling barrel; said traveling valve includes a seat
against which the ball is received, said traveling valve is mounted
on said traveling barrel at a location whereby said ball thereof is
lifted from the seat thereof by the free end of said pushrod during
each downstroke of the pump.
4. The gas release device of claim 1 wherein the downhole pump has
a traveling plunger, and means forming a valve cage which is
connected to provide said traveling valve assembly and to provide a
mount means for receiving the upper end of said main body of said
gas release device.
5. In a well pump for use in a wellbore, said pump having a pump
plunger mounted for reciprocating motion respective to a
cylindrical pump barrel, means imparting reciprocatory motion
between said plunger and barrel, there being a variable chamber
formed between the plunger and barrel for producing fluid
therethrough;
a traveling valve assembly having a caged ball element received
against a seat located therein for controlling fluid flow from the
variable chamber; and, a stationary valve assembly which is fixed
respective to the wellbore for controlling flow into the variable
chamber;
said stationary valve is operative on the downstroke to trap fluid
in the variable chamber of the pump and said traveling valve is
operative on the upstroke to lift fluid towards the surface; the
combination with said traveling valve of a gas equalizing
device;
said gas equalizing device includes a cylindrical housing having an
upper end attached to the lower end of the traveling valve
assembly, and a lower end spaced from said upper end, said
cylindrical housing has an axial bore which extends longitudinally
therethrough; an enlargement formed on the lower marginal end of
said cylindrical housing; circumferentially extending opposed
shoulders formed on said enlargement;
a piston having a cavity formed at an upper end thereof,
confronting circumferentially extending faces formed within said
cavity, and arranged for abuttingly engaging the opposed shoulders
of said enlargement of said cylindrical housing; whereby said
piston is loosely attached to said cylindrical housing and arranged
to reciprocate longitudinally respective thereto between the limits
provided by said confronting faces and said shoulders, a passageway
formed longitudinally through said piston and into said cylindrical
housing through which produced fluid can flow;
a pushrod having an upper marginal end portion telescopingly
received within the axial bore of the cylindrical housing and a
lower end portion rigidly attached to said piston; said piston
reciprocates towards and away from the traveling valve on the
downstroke and the upstroke; said upper end portion of said pushrod
has a terminal end which engages and lifts the traveling ball
element from its seat on the downstroke and which is moved free of
the traveling ball on the upstroke;
whereby; said pushrod has a free end that lifts the ball of the
traveling valve each downstroke of the well pump so that any
compressible fluid accumulated within the variable chamber is free
to flow from the variable chamber thereof.
6. The combination of claim 5 wherein said well pump has a
traveling plunger, said traveling valve is mounted on said
traveling plunger at a location whereby said ball thereof is lifted
from the seat thereof during each downstroke of the pump in the
aforesaid manner.
7. The combination of claim 6 wherein said equalizer device
includes an adaptor by which the traveling valve cage provides a
mount means by which said equalizer device can be attached
thereto.
8. The combination of claim 5 wherein said well pump includes a
traveling barrel; said traveling valve is mounted on said traveling
barrel at a location whereby said ball thereof is lifted from the
seat thereof during each downstroke of the pump in the before
described manner.
9. The combination of claim 8 wherein said equalizer device
includes an adaptor means connected to the traveling valve assembly
which provides a mount means for said device.
10. In an oil well having an artificial lift apparatus that
includes a downhole pump of the reciprocating type for lifting
fluid to the surface of the ground, said pump having a plunger, a
barrel, a variable chamber formed by the plunger and barrel; said
plunger being received within said barrel, means imparting
reciprocating motion between the plunger and barrel, a standing
valve and a traveling valve having a ball and seat for controlling
fluid flow through the variable chamber of the pump, the traveling
valve includes a valve cage, the combination with said pump of a
gas release device;
an adaptor connected to the traveling valve cage at the lower end
thereof by which said gas release device is mounted to said
traveling valve cage; said gas release device has a cylindrical
body having one end affixed to said adaptor and an opposed end
which extends towards the standing valve; a piston loosely captured
by said opposed end of said cylindrical body to thereby mount the
piston for limited reciprocating movement respective to said
cylindrical body;
a passageway formed through said piston and cylindrical body, and
along the central longitudinal axis of the pump barrel through
which produced fluid can flow, a pushrod having a free end
extending axially along the longitudinal axis of said cylindrical
body for engaging the ball of the traveling valve and a fixed end
which is attached to said piston whereby said pushrod is
reciprocatingly received in a captured manner within said
cylindrical body;
stop means within said piston for limiting the reciprocatory motion
of the piston respective to the cylindrical body;
said gas release device has only said piston, said cylindrical
body, and said pushrod; said piston comprises only a skirt member
and a port sub rigidly attached thereto, said port sub having an
upper face which forms one said stop means, a second stop means is
formed by the upper end of said skirt member; said skirt member has
an inwardly directed boss from which a circumferentially extending
downwardly directed cylindrical skirt extends, said passageway is
formed through said port sub for flow of production fluid directly
therethrough and to the traveling valve; said cylindrical body has
an outwardly directed enlargement formed at the lower end thereof
which is received within the upper end of said piston;
whereby; said piston moves the end of said pushrod into engagement
with the ball to thereby lift the ball of the traveling valve each
downstroke of the well pump.
11. The combination of claim 10 wherein said traveling valve is
mounted respective to said traveling plunger and to said pushrod
whereby said ball of said traveling valve is lifted from the seat
thereof during each downstroke of the pump, and the end of said
pushrod is spaced from said ball of said traveling valve on each
upstroke of the plunger.
12. The combination of claim 10 wherein said gas release device is
directly attached to said valve cage by said adaptor; said
cylindrical body is directly attached to said adaptor.
Description
BACKGROUND OF THE INVENTION
The production of crude oil often requires the use of artificial
lift means by which the crude oil is lifted from the bottom of the
borehole to the surface of the ground. Downhole pumps of the
reciprocatory type used downhole in a wellbore for lifting crude
oil from the bottom of the well thousands of feet to the surface of
the ground have been employed in the oil field for many years.
These downhole pumps are manufactured by a large number of
different firms and therefore the pumps take on a number of
different forms.
The produced fluid being lifted from the production zone always has
some compressible fluid, such as natural gas, solublized therein.
As the formation fluid migrates from the payzone, through the
casing perforations, and into the pump intake, separation between
the gaseous and liquid phase of the formation fluid often occurs.
Sometimes the separation is negligible and can thereore be ignored,
or at least tolerated; however, the separation of the gas and
liquid in most wells is considerable and brings about a condition
recognized in the oil field production art as "gas locking". Gas
locking is more likely to occur as the fluid level at the bottom of
the borehole is lowered due to the pumping action. This aspect of
downhole pumping, or artificial lift devices, and its deleterious
effect upon downhole equipment has been studied at great
length.
Most downhole pumps used in conjunction with pumpjack units have a
plunger attached to be reciprocated by a rod string. The plunger
has a check valve assembly, called a traveling valve assembly,
therein which controls the flow of formation fluid through the
plunger on the downstroke, and which closes to enable the plunger
to lift the fluid on the upstroke.
Other downhole pumps used in conjunction with pumpjack units have a
barrel attached to the sucker rod string while the plunger remains
stationary respective to the borehole. In this event, the
reciprocating barrel, has a traveling valve assembly associated
therewith which controls the flow of formation fluid through the
barrel.
In either event, it is advantageous to insure the ball of the
traveling valve assembly is lifted from its seat as the pump nears
the end of the downstroke, thereby expelling any compressible
fluids from the pump variable chamber and obviating gas locking.
This should not be confused with "fluid pounding" which results
from a pumped off condition, because nothing other than increased
flow from the production formation can avoid pumping off a
wellbore.
The patents to Simon U.S. Pat. No. 4,219,311; Ritchey U.S. Pat. No.
2,690,134; Patterson et al U.S. Pat. Nos. 2,344,786 and 2,344,787;
Hall U.S. Pat. No. 2,132,161; Streich U.S. Pat. No. 1,685,650;
Knotts et al U.S. Pat. No. 1,498,042; and Farrah U.S. Pat. No.
984,084 represent the pertinent prior art.
Ritchey '134 discloses a downhole pump having a traveling valve
element 44 which is upset from its seat by a finger 36. Note cage
30 attached to fixed plunger assembly 12, 20, 24, 26.
Hall '161 shows rod 11 guided at 10 and interposed between balls 6
and 13. Hence, the rod 11 is spring loaded by the lower ball spring
5.
Knotts, et al '042 discloses a finger movable against upper ball 7.
Note the spring in FIG. 2 which biases the finger downhole.
Patterson et al '786 and '787 shows a downhole pump having a
plunger 46 which is spring loaded and upsets upper ball 37.
None of the above patents show a pushrod attached to the traveling
valve of a downhole pump and means for moving the push-rod towards
the ball valve during the downstroke so that the ball is moved a
limited amount that cannot cause damage to the ball cage and which
exhausts compressible gases from the pump working chamber.
The various different solutions provided by the above prior art
references are deemed unsatisfactory, either because of their great
complexity and expense, or because of the inherent damage that can
potentially result as a consequence of the mechanism not being
properly adjusted as contemplated by the inventor. The employment
of apparatus thousands of feet downhole in a borehole cannot be
directly monitored and controlled once the apparatus is operating
out of sight and accordingly, it would be desirable to have made
available improvements in apparatus for preventing gas lock in
downhole pumps which avoid damage to the valve cage of the pump in
the event the apparatus and downhole pump are not precisely
adjusted to the optimum that may be desired.
SUMMARY OF THE INVENTION
This invention sets forth improvements in a gas relief device for
avoiding gas lock in a reciprocatory downhole pump. The apparatus
of the present invention is preferably used in combination with a
downhole production pump which is actuated by a string of sucker
rods connected to a pumpjack unit. The gas relief device of the
present invention is particularly useful in combination with a
downhole pump having a traveling valve and a fixed valve.
Broadly, the present invention comprises a device adapted to be
fitted to an ordinary downhole pump of the reciprocatory type, that
unseats the traveling ball check valve during most of the
downstroke. The device achieves this desirable result in response
to inertia, pressure differential of the produced fluid flow, and
friction between coacting parts of the pump and the device.
In particular, the novel gas relief device is positioned within the
downhole pump at a location adjacent the traveling valve, and
includes a piston member which is arranged to move a pushrod into
contact with and thereby unseat the traveling valve element from
the traveling valve seats as the pump reciprocates on the
downstroke. The piston member moves the pushrod free of the ball
check valve during the upstroke.
The relief device is positioned with the longitudinal axial
centerline thereof arranged to coincide with the longitudinal axial
centerline of the pump barrel and plunger. The device includes a
cylindrical housing mounted in fixed relationship respective to the
traveling valve of the pump. The housing is axially aligned with
the well tubing, with there being a piston having one marginal end
portion reciprocatingly received within the housing. One end of the
pushrod is connected to be moved by the piston so that a free end
portion extends uphole where it can be brought into contact with
the ball of the traveling valve assembly.
An adaptor sub formed at the upper end of the housing provides a
mounting means by which the device of the present invention can be
mounted and used in conjunction with a traveling plunger-type pump
or a traveling barrel-type pump.
Accordingly, a primary object of the present invention is the
provision of a gas relief device positioned within a downhole pump
and arranged to remove compressible fluid from the variable pump
chamber each downstroke of the pump.
Another object of the present invention is the provision of
apparatus for attachment to the valve cage of a downhole
reciprocatory production pump which opens the traveling valve each
downstroke of the pump.
A still further object of the present invention is the provision of
a gas relief device mounted in fixed relationship respective to a
traveling valve cage of a downhole production pump, wherein the
device is brought into contact with and lifts the ball of the
traveling valve assembly from its seat in response to inertia,
fluid flow, and friction each downstroke of the production
pump.
Another and still further object of the present invention is the
provision of method and apparatus by which pressure differential,
inertia, and friction are employed in a downhole pump to contact
and upset and ball of the traveling valve assembly each downstroke
of the pump.
An additional object of this invention is the provision of an
improved downhole pump gas release device which forms part of the
traveling valve assembly and includes a resilient extension
arranged along the longitudinal axis of the pump which is brought
into contact with the ball of the traveling valve assembly each
cycle of operation, and thereby avoids gas locking.
These and various other objects and advantages of the invention
will become readily apparent to those skilled in the art upon
reading the following detailed description and claims and by
referring to the accompanying drawings.
The above objects are attained in accordance with the present
invention by the provision of a combination of elements which are
fabricated in a manner substantially as described in this
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a part diagrammatical, part schematical, representation
of a cross-section of the earth, illustrating a prior art downhole
production pump actuated by a pumpjack unit, with apparatus made in
accordance with the present invention being associated
therewith;
FIG. 2 is an enlarged, fragmentary, part cross-sectional,
representation of part of the apparatus disclosed in FIG. 1;
FIG. 3 is an alternant embodiment of the apparatus disclosed in
FIG. 2;
FIG. 4 is an enlarged, longitudinal, part cross-sectional view of
part of the apparatus disclosed in FIGS. 1-3, with some parts being
removed therefrom, and other parts being shown so as to enhance
this disclosure; and,
FIG. 5 is an exploded view of the apparatus of the invention set
forth in FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1 of the drawings, there is diagrammatically illustrated a
prior art oil well production unit 10 which can take on many
different forms, and with which the present invention can
advantageously be used in combination therewith. The apparatus 10
includes a prior art pumpjack unit 12 which reciprocates a rod
string 14. The rod string 14 extends down through the illustrated
production tubing string 16, and the production tubing string 16
extends down through a cased borehole 18. A downhole oil well
production pump 20, which can be of several different
configurations, is supported within the tubing and the tubing is
supported from the casing 18 by any suitable apparatus 22. The
apparatus 22 can be a packer, a hanger, or other suitable support
means known to those skilled in the art.
Numeral 24 broadly illustrates the payzone or production formation
from which production fluid flows at 26 into the suction of the
downhole pump 28, whereupon the downhole pump 20 produces the fluid
by forcing the fluid to flow up the tubing string 16 and to the
illustrated wellhead. A gas relief device 34, made in accordance
with the present invention, is incorporated into the downhole pump
20, as will be more fully discussed hereinafter.
In FIG. 2, the production pump 20 is seen to be of the type having
a pump barrel 30 of the stationary type. The pump barrel 30 forms a
working chamber 31. The barrel 30 is mounted to tubing 16 by
support means 32. The support means 32 can take on any number of
forms and is well known to those skilled in the art. A standing
valve, schematically illustrated at 33, is located at the lower end
of the barrel 30. A gas relief device 34 of the present invention
is affixed to the lower end of the plunger 28 by means of the lower
end of a traveling valve assembly 36. Accordingly, the gas relief
device 34 of the present invention is fixed to the traveling valve
assembly and arranged in axial aligned relationship respective to
the pump barrel and plunger.
In FIGS. 2 and 4 of the drawings, there is disclosed a prior art
traveling valve cage assembly 36, which can take on a number of
different forms, and which allows the equalizer or gas release
device of the present invention to be suitably connected to the
downhole pump. The cage is attached to either a traveling plunger
or a traveling barrel as shown in the figures of the drawings. In
any instance, the equalizer is attached to the lower end of the
traveling valve of the pump as seen illustrated in the
drawings.
The equalizer 34 includes a piston 38 which reciprocates respective
to the traveling valve assembly 36. The pump suction 40 is
connected to the variable pump chamber 31 by means of the standing
valve assembly 33. Hence, stroking the pump causes formation fluid
at 26 to flow into suction 40, through the standing valve assembly
33, and into the pump variable chamber 31. Numeral 42 indicates the
produced fluid outlet, while numeral 44 indicates the box end of
the sucker rod string.
In FIG. 4, numeral 46 indicates the upper threaded end of the
traveling valve cage 36. The opposed lower end is threaded at 48,
and receives the upper threaded end 50 of an adaptor sub 52. The
adaptor sub 52 enables the present invention to be attached to any
valve cage 36. Numeral 54 indicates a seat against which the ball
56 of the check valve 36 is seated in sealed relationship
therewith. The ball is captured within the interior 58 of the valve
cage 36.
The equalizer 34 of the present invention is threadedly received at
60 by the adaptor 52. Hollow fixed body 64 has an enlargement 66
formed at the lower marginal end thereof. The piston 38 has an
internal circumferentially extending shoulder formed at 68 against
which shoulder 70 of the enlargement 66 abuttingly engages. The
terminal end of the enlargement forms a shoulder 72 which is
opposed to shoulder 70 and abuttingly engages the face 74 of port
sub 78. The upper marginal end of the port sub 78 is threaded at 76
and threadedly engages the piston 38 as illustrated at 75.
Lower face 80 of port sub 78 has a plurality of circumferentially
arranged ports 82 formed therein. The ports 82 are a series of
radially spaced, longitudinally extending passageways which
circumferentially extend about the axial centerline of the piston,
and in aligned relationship respective to a pushrod 84. The pushrod
84 has one end affixed to the central longitudinal axis of the port
sub 78. The upper terminal end 88 of pushrod 84 engages and lifts
ball 56 from seat 54 when piston 38 has reciprocated to its
uppermost limits during the downstroke of the plunger or barrel.
The terminal end 88 is positioned at a location approximately
1/16th inch below the ball 56 when the piston is reciprocated to
its lowermost position respective to the traveling valve cage 36
during the upstroke of the plunger or barrel.
The variable pump chamber 31 receives formation fluid which flows
through suction 40, through the standing valve 33, and into the
variable chamber 31. As the pump is reciprocated by the pumpjack,
fluid is sucked into the variable pump chamber 31 on the upstroke
and is forced through the traveling valve 36 on the downstroke so
that fluid flows into the annulus between the downhole pump and the
tubing string 16.
Accordingly, fluid must flow into the passageways 82 of the
equalizer, into the annulus 90 formed between the pushrod 84 and
the hollow main body 64, through the valve seat 54, about the ball
56 which must be lifted from the seat at this time, through the
valve cage 36, and into the before mentioned production tubing.
Accordingly, it is necessary that the piston 38 be reciprocated in
response to reciprocal motion induced into the pump assembly as the
pump upstrokes and downstrokes. As the pump downstrokes, the piston
38 moves uphole respective to the valve cage 36. This movement is
effected by inertia, pressure differential across the port sub 78
due to fluid flowing through passageways 82, and friction between
the outer surface of the piston and the inner surface of the pump
barrel. This action moves the piston of the equalizer assembly
uphole respective to the traveling valve at the beginning of the
downstroke so that any compressible fluid that may accumulate
within the variable pump chamber 31 is exhausted from the variable
chamber as soon as it accumulates therein, thereby avoiding gas
lock or fluid pounding until the well has pumped off.
In the absence of the present invention, it is possible for some
walls to become gas locked prior to a pump-off condition being
encountered. Such a condition is possible due to accumulation of
compressible fluid within the variable chamber 31 of the downhole
pump. Once a pump has become gas locked, it is sometimes necessary
for an expert to remedy the situation or otherwise, the pump cannot
produce fluid.
* * * * *